The present invention concerns continuous-transport developing machines for photographic emulsion carriers of the type including at least one tank filled with processing fluid, to which regenerating fluid must be continually added to maintain the chemical activity of the processing fluid. The replenishing means used to supply the regenerating fluid typically comprises a dosing valve provided with a flow meter and a supply tank containing regenerating fluid and supplying such fluid to the dosing valve.
With continuous-transport developing machines of the type in question, because of the high rate at which photographic emulsion carrier is transported through the machine, the rate at which regenerating fluid must be added to the processing-fluid tanks is quite high. For this reason, the regenerating fluid is typically kept in relatively large supply tanks and from there directly fed to the processing-fluid tanks to be replenished. For reasons of limited space availability, it is often necessary that these large supply tanks be located relatively distant from the processing-fluid tanks which they are to replenish, the regenerating fluid then being fed to the dosingvalves for the processing-fluid tanks by reliance on gravity descent or utilizing pumps. In either case, the pressure just upstream of the dosing valve fluctuates very considerably in dependence upon the extent to which the supply tank is filled with regenerating fluid at any particular time. As a result, in order to achieve high-precision dosing of regenerating fluid, it becomes necessary to provide the dosing valve with negative-feedback volumetric flow rate control means, or else to frequently readjust the dosing valve as the supply tank continually empties.